Skin cancer is the most common malignancy in man. Incidence rises sharply with age and strongly linked to UV radiation exposure. The predisposing factors of advanced patient age and known environmental carcinogens make skin cancer an extremely important model in which to study the complex cellular and molecular events underlying malignant transformation generally. The long term goal of these studies is to critically examine the biologic responsiveness and genetic regulation of malignant cells derived from cutaneous squamous cell carcinomas (SCC) wit normal epidermal keratinocytes derived from adjacent sun exposed and sun protected sites of the same individuals and from healthy newborns. Using sophisticated tissue culture techniques we will examine the effect of known modulators of keratinocyte growth and differentiation on the expression of specific genes and their protein products potentially involved in these processes. Specifically the effect of epidermal growth factor, serum, strontium, calcium, and interferon on keratinocyte proliferative capacity and differentiation will be determined using the appropriate techniques. We will subsequently check the possibility of rearrangement, amplification or mutations of specific proto-oncogenes in SCC cells, adjacent sun exposed and sun protected areas statistically predisposed to malignancy and newborn keratinocytes using Southern blot analysis a well as DNA amplification and sequencing. We will ultimately attempt to transfect the C-Ki-ras or other implicated oncogenes(s) into cultured human keratinocytes to determine whether the oncogene alone or in combination with UV radiation can transform the cells, and further test the hypothesis that retinoids can alter biologic responsiveness and gene expression of cells using the same techniques. In this way we hope to construct a model of normal human keratinocyte growth and differentiation in vitro, top elucidate the mechanisms involved in development of SCC and to determine whether retinoids exert a protective effect in this model.